Synthesis and Characterization of N‐methylenephenyl Phosphonic Chitosan

Chitosan is a natural based polymer obtained by alkaline deacetylation of chitin, exhibiting excellent properties such as non‐toxicity, biocompatibility and biodegradability. N‐Methylenephenyl phosphonic chitosan (NMPPC) is synthesized from chitosan by reacting with phenyl phosphonic acid using formaldehyde. The NMPPC was characterized by FTIR, ³¹P‐NMR, X‐ray diffraction, scanning electron microscopy, thermogravimeteric analysis and solubility studies. A significant decrease of molecular weight was observed in the NMPPC. The TGA studies suggested that NMPPC has less thermal stability than chitosan. The X‐ray diffraction analysis showed that NMPPC was amorphous in nature. The solubility property of the polymer was improved after the incorporation of a phenyl phosphonic group.     

Synthesis and Characterization of a Novel Liquid Crystalline Chitin — Quaternary Ammonium Chitosan Salt

N-Butyl chitosan(NBCS) derivatives were prepared by introducing butyl groups into the amine groups of chitosan via Schiff base intermediates. The quaternization of NBCS was carried out by using ethyl iodide to produce water-soluble cationic polyelectrolytes. The degree of the substitution of the products was measured by means of the electron spectroscopy for a successful chemical analysis. The quaternary ammonium chitosan salt(QACS) was proved to be a novel cholesteric liquid crystalline chitin, by means of the polarized optical microscopy and the circular dichroism spectropolarimetry. The critical mass fraction of the QACS/formic acid solution forming a lyotropic liquid crystal phase was 50%, which was almost the same as that of the NBCS/formic acid solution, but much hiuher than that of the chitosan in the same solvent.     

6-O-（Hydroxypropyltrimethylammonia）-β-cyclodextrin with Low Degree of Substitution： Convenient Preparation and its Application as a Chiral Selector in Capillary Electrophoresis

Cyclodextrins (CDs) have been widely used as host compounds in molecular recognition, chiral separation and enzyme models1,2. For constructing additional potential host models, research has focused on the regioselective functionalization of nature CDs, wh…     

Characterization and classification of stationary phases in HPLC and SFC – a review

Packed column supercritical fluid chromatography (pSFC) is an attractive technique in drug discovery related analysis because it offers several advantages over the more commonly used high-performance liquid chromatography (HPLC) technique. The environmental-friendly CO₂ mobile phase, the high-throughput capacity, the increased efficiency and the lower operational costs give SFC additional benefits over HPLC in analysis related to drug development. The latter technique is well established and has been used for decades in the pharmaceutical industry. On the other hand, SFC is still in its infancy, even though the technique has been known for decades and researchers are still discovering the possibilities and limitations of this technique.     

Instrumented Macroindentation Techniques for Polymers and Composites – Mechanical Properties,Fracture Toughness and Time-Dependent Behaviour as a Function of the Temperature

An innovative cooling and heating device has been successfully applied to an instrumented macrohardness testing machine in close collaboration with the company Zwick/Roell. The prototype allows the local time-dependent analysis of mechanical properties such as Martens hardness and indentation modulus, as well as fracture toughness and creep and relaxation behaviour at temperatures ranging from −100 °C to +100 °C. On the basis of load–indentation depth, load–time or indentation depth–time diagrams, the indentation behaviour as a function of test speed and/or temperature (which has rarely been done for polymers in the macro-range of loading) depending on matrix and materials composition (amorphous/semicrystalline thermoplastics, epoxy resins, micro- and nanocomposites) has been analysed. Martens-hardness, indentation modulus on the one hand and creep compliance and relaxation modulus on the other have been found to be strongly temperature dependent. Adequate methods of indentation fracture mechanics have been enhanced for polymers and applied to determine the fracture toughness of very different polymer-based materials.     

Estimates of Internal Pressure and Molar Refraction of Imidazolium Based Ionic Liquids as a Function of Temperature

Estimates of the internal pressure (∂ U/∂ V) _T of the ionic liquids (ILs) 1-butyl-3-methylimidazolium tetrafluoroborate [BMIM][BF₄], 1-butyl-3-methylimidazolium hexafluorophosphate [BMIM][PF₆], and 1-methyl-3-octylimidazolium tetrafluoroborate [OMIM][BF₄] were made from experimentally determined densities and speeds of sound in the temperature range 283.15 to 343.15 K. Values (∂ U/∂ V) _T for all the ILs studied are higher than those of water and molecular organic liquids. We also measured the refractive indices n _D in the temperature range 288.15 to 343.15 K and estimated the molar refraction R _M. Refractive indices of ILs were also higher than those of normal organic liquids but were comparable to those of long hydrocarbon chain organic solvents.     

Photo-induced Synthesis and Characterization of Poly（methyl methacrylate） Grafted Sodium Salt of Partially Carboxymethylated Guar Gum

Photo-induced graft copolymerization of methyl methacrylate（MMA） onto sodium salt of partially carboxymethylated guar gum（Na-PCMGG, DS = 0.291） was carried out in an aqueous medium using ceric ammonium nitrate（CAN） as photoinitiator to synthesize a novel graft copolymer, Na-PCMGG-g-PMMA, which may find its potential application as a metal adsorbent. The influences of synthesis variables such as concentrations of photoinitiator（CAN）, nitric acid and monomer（MMA） as well as reaction time, temperature and amount of substrate on the grafting yields were studied and the reaction conditions for optimum photo-grafting were evaluated. At optimum concentration, the maximum values of the grafting yields achieved were G = 271.61% and GE = 63.89%. The experimental results were found to be in very good agreement with the proposed kinetic scheme. The photo-graft copolymerization of MMA onto Na-PCMGG（ DS = 0.291） was also carried out in the presence and absence of ultraviolet radiation for studying the efficiency of the photoinitiator. The influence of carboxymethyl groups introduced onto the guar gum molecules with regard to its behavior towards ultra-violet radiation induced grafting with MMA was also investigated. Photo-grafting process was confirmed and the products were characterized with the help of the spectroscopic（1H-NMR and FTIR） and SEM techniques.     

Oxidative Condensation of Methane on Sr2 –xLaxTiO4 Catalysts: Effect of the Degree of Substitution of Sr and La

Kinetics and Catalysis - The Sr2 –xLaxTiO4 (x = 0–2.0) catalysts were synthesized based on strontium titanate with a layered perovskite structure. The effect of the degree of...     

Isomorphous Substitution of Aluminium for Gallium in a Framework Gallophosphate

An aluminium-substituted framework gallophosphate with occluded triethylamine was synthesized hydrothermally. 27Al MAS NMR spectroscopy indicates that only the tetrahedral coordinated gallium atoms in the gallophosphate are substituted by aluminium atoms. The substitution leads to an evident decrease in cell volume of the crystal. The differences between the original gallophosphate and the aluminium-substituted one are also found for the IR spectrum and the thermal property.     

Multigram Synthesis of a Combustion-Relevant δ-Ketohydroperoxide through Sulfonylhydrazine Substitution

A synthesis of a δ-ketohydroperoxide is described, addressing potential functional-group compatibilities in these elusive species relevant to combustion and atmospheric chemistries. The hydroperoxide is installed via sulfonylhydrazine substitution, which was found to be more effective than displacement of secondary halides. As part of this protocol, it was observed that 1,2-dimethoxyethane is an advantageous medium for the reaction, avoiding the formation of a tetrahydrofuran hydroperoxide side product. This discovery facilitated the multigram synthesis (6 steps, 41 % yield overall) and discrete characterization of the target δ-ketohydroperoxide.     

Preparation and Characterization of Chitosan Composite Membranes Crosslinked by Carboxyl-capped Poly（ethylene glycol）

In this study a series of chemically crosslinked chitosan/poly（ethylene glycol） （CS/PEG） composite membranes were prepared with PEG as a crosslinking reagent other than an additional blend. First, carboxyl-eapped poly（ethylene glycol） （HOOC-PEG-COOH） was synthesized. Dense CS/PEG composite membranes were then prepared by casting/evaporation of CS and HOOC-PEG-COOH mixture in acetic acid solution. Chitosan was chemically crosslinked due to the amidation between the carboxyl in HOOC-PEG-COOH and the amino in chitosan under heating, as confirmed by FTIR analysis. The hydrophilicity, water-resistance and mechanical properties of pure and crosslinked chitosan membranes were characterized, respectively. The results of water contact angle and water absorption showed that the hydrophilicity of chitosan membranes could be significantly improved, while no significant difference of weight loss between pure chitosan membranes and crosslinked ones was detected, indicating that composite membranes with amidation crosslinking possess excellent water resistanance ability. Moreover, the tensile strength of chitosan membranes could be significantly enhanced with the addition of certain amount of HOOC-PEG-COOH crosslinker, while the elongation at break didn＇t degrade at the same time. Additionally, the results of swelling behaviors in water at different pH suggested that the composite membranes were pH sensitive.     

Alkylation of Nitroarenes via Vicarious Nucleophilic Substitution – Experimental and DFT Mechanistic Studies

Alkylation of nitroarenes via Vicarious Nucleophilic Substitution (VNS) was tested experimentally and modelled with DFT calculations. Mechanistic studies reveal intrinsic differences between reactions of archetypal carbanion precursor PhSO₂CH₂Cl, and alkyl phenyl sulfones, in which benzenesulfinate acts as a leaving group. Accordingly, for the latter precursors steric hindrance develops at the β-elimination step, that raises energy barrier and results in the formation of byproducts.     

Benzosuberyl Substituents as a “Sandwich-like” Function in Olefin Polymerization Catalysis

For the rational design of metal catalyst in olefin polymerization catalysis, various strategies were applied to suppress the chain transfer by bulking up the axial positions of the metal center, among which the "sandwich" type turned out to be an efficient category in achieving high molecular weight polyolefin. In the α-diimine system, the "sandwich" type catalysts were built using the typical 8-aryl-naphthyl framework. In this contribution, by introducing the rotationally restrained benzosuberyl substituent into the ortho-position of N-aryl rings, a new class of "sandwich-like" α-diimine nickel catalysts was constructed and fully identified. The rotationally restrained benzosuberyl substituents played a "sandwich-like" function by capping the nickel center from two axial sites. Compared to the nickel catalyst Ni1 bearing freely rotated benzhydryl substituent, Ni2 featuring benzosuberyl substituent enabled the increase(8 times) of polymer molecular weights from 8 kDa to 65 kDa in the polymerization of ethylene. By further increasing the steric bulk of another ortho-site of the N-aryl ring, the polymer molecular weight even reached an ultrahigh level of 833 kDa(M_w=1857 kDa) using the optimized Ni3. Notably, these nickel catalysts could also mediate the copolymerization of ethylene with methyl 10-undecenoate, with Ni3 giving the highest copolymer molecular weight(88 kDa) and the highest incorporation of comonmer(2.0 mol%), along with high activity of up to 10~5 g·mol~(-1)·h~(-1).     

Synthesis and Characterization of a Novel Galactosylated Cholesterol

Mammalian hepatocytes (parenchymal cells) exclusively possess large number ofasialoglycoprotein receptors (ASGPr), which can recognize terminal D-galactose orN-acetylgalactosamine residues. Lactobionic acid 1, bearing a galactosyl group, isusually used as…     

Chemically Modified Chitosan Beads as Molecularly Imprinted Polymer Matrix for Adsorptive Separation of Proteins

In a phosphate buffer, a hemoglobin (Hb)-imprinted polymer complex was preparedusing maleic anhydride (MAH) modified chitosan beads as matrix, acrylamide (AM) as functionalmonomer, N,N-methylenebisacrylamide (MBA) as cross-linker and potassiumpersulfate (KPS) /sodium hydrogen sulfite (NaHSO3) as initiators. Langmuir analysis showed that an equal class ofadsorption was formed in the molecular imprinting polymer (MIP), and the MIP has highadsorption capacity and selectivity for the imprinted molecule. The MIP can be reused and therecovery was approximately 100% at low concentration.     

Organic Solvent Tolerance of an α-Amylase from Haloalkaliphilic Bacteria as a Function of pH,Temperature, and Salt Concentrations

A haloalkaliphilic bacterium was isolated from salt-enriched soil of Mithapur, Gujarat (India) and identified as Bacillus agaradhaerens Mi-10-6₂ based on 16S rRNA sequence analysis (NCBI gene bank accession, GQ121032). The bacterium was studied for its α-amylase characteristic in the presence of organic solvents. The enzyme was quite active and it retained considerable activity in 30% (v/v) organic solvents, dodecane, decane, heptane, n-hexane, methanol, and propanol. At lower concentrations of solvents, the catalysis was quite comparable to control. Enzyme catalysis at wide range of alkanes and alcohol was an interesting finding of the study. Mi-10-6₂ amylase retained activity over a broader alkaline pH range, with the optimal pH at 10–11. Two molars of salt was optimum for catalysis in the presence of most of the tested solvents, though the enzyme retained significant activity even at 4 M salt. With dodecane, the optimum temperature shifted from 50 °C to 60 °C, while the enzyme was active up to 80 °C. Over all, the present study focused on the effect of organic solvents on an extracellular α-amylase from haloalkaliphilic bacteria under varying conditions of pH, temperature, and salt.     

Synthesis and MALDI-TOF Characterization of β-CD Core ATRP Initiators and RAFT Chain Transfers with Different Degrees of Substitution

In this paper, three different kinds of β-CD derivatives were synthesized as atom transfer radical polymerization(ATRP) initiator or reversible addition-fragmentation chain transfer polymerization(RAFT) chain transfers. The degree of substitution for each derivative was carefully characterized through 1H-NMR, 13C-NMR spectroscopy and matrix-assisted laser desorption/ionization time of flight mass spectrometry(MALDI-TOF-MS). The factors influencing the degree of substitution were discussed. Moreover, the comparison between ATRP and RAFT was shown in the polymerization of Nisopropyl acrylamide(NIPAM).